Firefox provides a set of keyboard shortcuts that allow you to perform common tasks quickly.
You can open and close windows and tabs, navigate through pages and open tabs, create bookmarks, open history, zoom in and out, and much more, with just a few keystrokes.
For those of you unfamiliar with how keyboard shortcuts work, I would recommend reading my introduction to the subject really quick.

Firefox add-ons are applications that allow you to enhance your browser by adding functionality and style.
A browser is the computer program that you use to browse the internet.